<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script>
        function recursion(n) {
          if (n < 0) {
            return '输入的数字不能小于0';
          } else if (n == 0) {
            return 0;
          } else if (n == 1) {
            return 1;
          } else if (n > 1) {
            return recursion(n - 1) + recursion(n - 2);
          }
        }
        console.log(recursion(10));
      </script>